03 Nov 2013

Source: PAtrees.org

Trees play an incredible role in reducing stormwater in several ways and removing or filtering pollutants that would otherwise wind up in our waterways.

Interception    Tree canopies intercept and capture rainfall, reducing the amount that reaches the ground. In urban and suburban settings, a single deciduous tree can intercept between 500 and 760 gallons per year, while a mature evergreen can intercept over 4,000 per year.

Soil Infiltration     Tree roots allow for better infiltration of rainfall with rates of up to 15 inches per hour. The leaf acts as a sponge, allowing for slow infiltration into soils before releasing it to natural channels and recharging ground water.

Evapotranspiration     Trees consume stormwater through a process called evapotranspiration. Water is taken up by roots and move up through the tree until it is transpired back into the atmosphere as water vapor. A single mature oak tree can consume (transpire) over 40,000 gallons of water each year.

Phytoremediation     Trees are very good at removing pollutants such as nitrates & phosphates; and other contaminates such as heavy metals, pesticides, solvents, oils, and hydrocarbons that are found in stormwater.

Riparian Buffers      Trees protect and buffer streams and are critical to maintaining healthy, clean streams. Tree roots provide streambank stability, reducing erosion, filter out sediments, remove nutrients, shade and cool the water, provide habitat for many different species, and provide the primary food source for aquatic insects that are a critical part of the aquatic food chain.